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authorJoerg Roedel <joerg.roedel@amd.com>2011-03-25 09:44:48 +0100
committerAvi Kivity <avi@redhat.com>2011-05-11 07:57:04 -0400
commit8f6055cbaf68cbd9ff2692a2cfa691b43629ccd4 (patch)
treee178845f4d0f061f90e57337f28be6640da8bd6d /arch/x86/kvm/x86.c
parent1e993611d0dc879fde25515dc9867d1cfd4c5137 (diff)
KVM: X86: Make tsc_delta calculation a function of guest tsc
The calculation of the tsc_delta value to ensure a forward-going tsc for the guest is a function of the host-tsc. This works as long as the guests tsc_khz is equal to the hosts tsc_khz. With tsc-scaling hardware support this is not longer true and the tsc_delta needs to be calculated using guest_tsc values. Signed-off-by: Joerg Roedel <joerg.roedel@amd.com> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/x86/kvm/x86.c')
-rw-r--r--arch/x86/kvm/x86.c9
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 78d729174d99..fcce29b7b6fa 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2113,8 +2113,13 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
kvm_x86_ops->vcpu_load(vcpu, cpu);
if (unlikely(vcpu->cpu != cpu) || check_tsc_unstable()) {
/* Make sure TSC doesn't go backwards */
- s64 tsc_delta = !vcpu->arch.last_host_tsc ? 0 :
- native_read_tsc() - vcpu->arch.last_host_tsc;
+ s64 tsc_delta;
+ u64 tsc;
+
+ kvm_get_msr(vcpu, MSR_IA32_TSC, &tsc);
+ tsc_delta = !vcpu->arch.last_guest_tsc ? 0 :
+ tsc - vcpu->arch.last_guest_tsc;
+
if (tsc_delta < 0)
mark_tsc_unstable("KVM discovered backwards TSC");
if (check_tsc_unstable()) {